1. Technical Field
The present invention relates to a light guide member, and an object detection apparatus having the light guide member, and a vehicle.
2. Background Art
Object detection apparatuses for detecting an object (e.g., raindrop) adhered on a surface of a light translucent member (e.g., windshield) composing a vehicle are known.
The object detection apparatus includes, for example, a light source such as a light emitting element that emits light to irradiate an object, and a detection unit such as a light receiving element to receive reflection light reflected from the object and to detect the object based on change of light quantity of the received reflection light.
The object detection apparatus includes, for example, a light guide member made of translucent material, disposed between the light translucent member (e.g., windshield), and the light source and the detection unit to guide light exiting from the light source and reflection light reflected from an object.
As to the object detection apparatus including the light guide member, to avoid false detection of an object, it is required that air bubble does not exist between the light guide member and the light translucent member.
In view of this, when installing the object detection apparatus, adhesive material such as adhesive layer or adhesive sheet may be disposed between the light guide member and the light translucent member to prevent intrusion of air bubble between the light guide member and the light translucent member as disclosed in JP-H11-304700-A and JP-2000-131231-A.
Typically, a windshield attached with the object detection apparatus has a three-dimensional curved face in line with a designed shape of a vehicle.
As to conventional object detection apparatuses, because a shape of the windshield and a shape of contact face of the light guide member are different, when the light guide member is attached to a three-dimensional curved face of the windshield, air bubble may intrude between the adhesive and the windshield and/or between the adhesive and the light guide member.
As to conventional object detection apparatuses, the light guide member is contacted to the windshield, which is a three-dimensional curved face, via adhesive material. To facilitate efficiency of attachment work, the light guide member is fixed to the windshield via an adhesive sheet having higher flexibility.
However, the adhesive sheet having higher flexibility deforms easily. For example, when inertia force effects to the light guide member due to acceleration/deceleration or vibration of a vehicle, the adhesive sheet deforms, with which the relative position of the light guide member with respect to the vehicle may deviate or fluctuate.
If the relative position of the light guide member with respect to the vehicle deviates or fluctuates, the relative position of the light guide member with respect to the windshield, the detection unit, and the light source configuring the object detection apparatus deviates or fluctuates, with which light quantity detected by the detection unit may change or fluctuate.
As to the object detection apparatus, adhered object such as raindrop is detected based on change of light quantity detected by the detection unit. If inertia force effects to the light guide member when an object does not adhere on the windshield, the object detection apparatus may falsely detect that an adhered object exists, with which detection precision deteriorates.
Detection sensitivity of the adhered object can be improved by enlarging a detection area of adhered object. To enlarge detection area of adhered object, an area of the adhesive sheet configuring a contact face contacted to the windshield is required to be greater.
To contact the light guide member to the windshield having the three-dimensional curved face via the adhesive sheet, the adhesive sheet having higher flexibility is required to be used. Therefore, as to the object detection apparatus attachable to the windshield having the three-dimensional curved face via the light guide member, when inertia force effects to the light guide member, detection precision of the adhered object may deteriorate as described above.